If you get the email, you are good, else check your server email.
If you got the email from the test script and you still get "Cannot Send Email: Internal Error" then it might be your file permissions. Make sure that directory permission is not 777, change it to 755 and test it.

You should be fine.
Also please rate us a 5 star if you like this plugin

Had the Internal error.
The issue on my Windows v-box was, that checkdnsrr is undefined in my PHP version.
I modified the plugins code to check for the availability of the function before calling it to double check the mail address.